probably at the moment it's best to stick with algo compression for bass. i've seen a few things that seem possibly promising with nebula and bass compression, but it's really too early for me to say for sure, and the problem will be making sure it's consistent. it also seems to involve several different things so it's not just a simple adjustment.
Where it seems to be a limitation is where Nebula truly shines. Let Nebula gives the tone and attitude and let algo comp do the control.
For rock/metal basses, try splitting signal on 2 channels and control signal w algo comp before Nebula instances. On bus(drums+bass,guitars,vocals,backing,keys), always put nice Nebula comp (barely compressing) or MOJO from HO or CDSM (DBX160) for attitude. On // compression channels, crushing signal then going into Nebula comp then Nebula EQ is great.
When you have a nice balance, put everything in time mode or load the corresponding presets and render. (Cupwise SHQ and Gemini NC products really shines at this game.)